Method of diamond heat treatment

FIELD: process engineering.

SUBSTANCE: invention relates to processes used in operation at high pressure and modifying substances physically. Proposed method comprises placing diamond in reaction cell in pressure transmitting medium, increasing pressure in reaction chamber and it cooling. Note here that thermal treatment is carried out at temperature increase rate of 10-50°C/s and at 2000-2350°C by passing electric current via heater in cell from programmed power supply source with due allowance for temperature relaxation in said cell in heating. For this, note also that temperature relaxation constant is defined. Said cell is cooled after heating by switching off power supply in forming short diamond heating pulse in temperature range of over 2000°C with diamond total stay time smaller than 30 seconds. Allowance for temperature relaxation in said cell in heating for heating rate Vt and pre-definition of cell temperature relaxation constant τ is made by setting in said programmable power source the maximum temperature of heating to τVT above maximum treatment temperature of 2000-2350°C.

EFFECT: changing colour of low-grate natural diamond without notable graphitisation, high-quality gem diamonds.

2 cl, 5 dwg, 3 ex

 

The invention relates to methods used when working with high pressure and causing physical modification of substances. The proposed method is designed to change the color of diamond and improve their quality, in particular to change brown natural diamond crystals under high temperature under high pressure in the metastable existence of the diamond on the phase diagram of carbon.

A known method of improving the mechanical properties of CVD-diamond (crack resistance) by annealing at temperatures in the range 1100-2200°C in an inert atmosphere at low pressure in a short period of time, which decrease with increasing annealing temperature so as to prevent graphitization specified diamond (Anthony et al. Method for enhancing the toughness of CVD diamond. - US Patent Number: 5451430, Int. Cl.: B05D 3/02. Date of Patent: Sep.19, 1995). In the method the relation between the parameters of heat treatment: temperature annealing and limit the duration of annealing at which ensured the safety of the diamond. For example, to temperatures of about 1600°C. the duration of the annealing should be less than 10 minutes and to a temperature of about 1900°C. is less than 15 seconds. In this method, heat treatment of diamond is carried out in the region of thermodynamic stability of graphite on the phase diagram of carbon without the use of the equipment is tov high pressure, and it is aimed only at removing non-uniform stresses in the crystal lattice CVD diamond that arise in its cultivation, and not to change the color of natural diamonds.

There is a method of annealing the single crystal diamond obtained CVD method at a high rate of growth of the single crystal, with the aim of improving its optical purity by heating the diamond to a predetermined temperature, comprising at least 1500°C., at a pressure equal to at least 4 GPA (Hemley et al. Annealing the single crystal Chemical Vapor Deposition diamonds. US Patent Application Publication No.: 2007/0290408, Int. Cl.: B29C 71/02. Pub. Date: Dec. 20, 2007). According to the description of the invention are grown at high growth rates of CVD diamonds can acquire a brown color, but with the heat treatment in the reaction cell of the high-pressure apparatus (temperature 1800-2900°C, a pressure of 5-7 GPA and time 1-60 minutes) they can be turned into colorless single crystals of diamond. In this method, the annealing process is carried out in the region of thermodynamic stability of graphite on the phase diagram of carbon, or in the region of thermodynamic stability of diamond near the line of the graphite-diamond equilibrium line on a chart. The method allows to achieve a higher annealing temperatures compared with the previous analogy, since the heat treatment of diamond is carried out at high pressures. But the question of the prevention of possible g is faisali diamond when processing in its metastable state in the description of the invention is not considered. It is noted only that the reaction cell must be cooled before unloading apparatus to ensure that the diamond was not graphite. The main disadvantage of the method is that it is designed only for annealing of synthetic CVD diamond having, as a rule, small.

The closest technical solution to the claimed invention is a method of changing the color of dyed natural diamonds (Vagarali et al. High pressure/high temperature production of colorless and fancy-colored diamonds. - US Patent No.: 7323156 B2, Int. Cl. C01B 31/06, B01J 3/08. Date of Patent: Jun. 29, 2008), which can be used to obtain a diamond of the finest quality jewelry from low-grade natural diamond brown color. The method is used the office of the high pressure and high temperature, and the parameters of thermobaric treatment of diamond crystals (pressure, temperature and time) can vary within wide limits: pressure from 10 to 200 kbar, the temperature is from 1500 to 3500°C., the holding time is from 30 seconds to 96 hours. Weight natural diamond may be in the range from 0.1 to 100 carats. In the method, the reaction cell is pressed into the capsule diamond is subjected to the action of high pressure and high temperature or stability of graphite on the phase diagram of carbon for a time sufficient to change the color of a diamond without significant graphitization, or is above the equilibrium line of the diamond-graphite in the field of diamond stability in the phase diagram of carbon, where there are no restrictions on the duration of the high-temperature stage of the annealing process. (Line balance diamond-graphite phase diagram of carbon can be set by the equation: P=19,4+0,025 T, where the pressure P is measured in kilobar, and the temperature T in degrees Celsius; so that in the coordinate plane with axes T and P above this line is the region of stable existence of the diamond, and below this line is the region of stable existence of graphite. Phase transition of graphite-diamond has a wide area of the metastable coexistence of the phases on either side of the equilibrium line on the chart.) In the description of the invention it is noted that work in the field of stability of graphite sensitive to the time factor and should carefully monitor the period of time during which the diamond is subjected to high temperature heating in this area. The period should be sufficiently long so that the color of a diamond has improved, but not so long that the diamond when processing was gravitationally. Pets partial graphitization diamond, but with significant graphitization in the description of the invention I propose to compare the decrease in the price of the diamond from losing its weight and increase its price reached in the result of changing its color, so as not to be a loser.

The main disadvantage of this method is that str is both in the processing of diamond crystals in the field of stability of graphite do not take into account the influence of the heating rate of the cell and the nature of the relaxation temperature in the chamber when changing the heating power on the attainable temperature in the cell and the duration of the period of time when the diamond is in the high-temperature treatment area. In no way can define or control the temperature in the cell by brief heating, which increases the risk of graphitization of diamond crystals. (Below in the description of the invention is illustrated, how would you describe the relaxation of the temperature in the reaction cell of the high-pressure chamber when changing the heating power.)

The present invention is directed to improving the reliability of the process of thermal processing of natural diamonds brown in the high-pressure stability of graphite on the phase diagram of carbon.

This is achieved by the fact that the process is performed at a pressure in the range of 3-6 GPA, and heating the reaction cell of a high pressure is carried out at the speed of rise of temperature 10-50°C/s to a temperature in the range 2000-2350°C by passing an electric current through the heater cells from the programmable power supply, taking into account the relaxation of the temperature in the cell and subsequent rise of temperature from the sudden cooling of the cell by turning off the heating power, forming a short pulse heating of a diamond with a total time of finding a diamond in the zone temperatures above 2000°C in less than 30 seconds. On diameterically processing the proposed method is a process of hardening materials, followed by rapid cooling, and not to the annealing of materials followed by their exposure at high temperature and slow cooling. The proposed method solves the problem of short-term high-temperature heating of the diamond with the change of its color and without graphitization in a high pressure chamber with a large reaction volume. Upper limit of the applied pressure due to the fact that the method is carried out in the cells of large volume, in which pressures above 6 GPA uneconomical. The lower limit of the range of applied pressures, 3 HPa, due to the possible grafitizare diamond at high temperatures at lower pressures. The lower bound of the temperature range determined experimentally at temperatures below 2000°C., as a rule, observed only a partial weakening of brown crystals of diamond-related physical classification of type IIA. At temperatures above 2350°C was observed surface graphitization of diamond crystals or blackening foreign inclusions that may be present inside the crystals. The lower limit of the speed of temperature rise due to the fact that at low speeds, less than 10°C/s, can significantly increase the residence time of the processed diamond crystal in the zone of high temperatures, which increases the risk of graffiti is then, and a higher heating rate (50°C/s) reaction cell in the cells of large volume can be realized only when too powerful power supply. The limit on the total time (30 seconds) find the diamond in the zone temperatures above 2000°C is associated with a high risk of surface graphitization of diamond, observed for a longer stay of diamond crystals in this zone. The method requires a prior camera calibration temperature under quasi-stationary conditions and determine the time constant of the temperature relaxation in it. This significant parameter, the characteristic time of thermal relaxation in the cell depends on the temperature in the reaction cell by brief heating, was not taken into account earlier in thermobaric diamond processing in high-pressure devices.

The invention is illustrated by drawings and schedules, figure 1-5.

Figure 1 is a cross section presents a high-pressure apparatus (the Central part) and the design of the reaction cell, which was used for process temperature treatment of diamond crystals on the proposed method. (Detailed information about the device can be found in the description of the invention: Nikolaev, N.A., Shalimov PPM "Device for creating ultra-high pressure and temperature", patent of Russian Federation №1332598 from 02.02.1993.) The device is placed against each other profiled matrix 1 and 1', made of solid alloy. Between matrices is a container 2 made of a lithographic stone. In the Central hole of the container placed in the reaction cell containing tubular graphite heater 3, the outer heat insulating sleeve 4 and the inner insulating tablets 5 and 5', pressed from a mixture of powders of NaCl and ZrO2; inside the heater is a cylindrical capsule 6, wherein in the manufacture of pressed from a powder of hexagonal boron nitride is placed crystal diamond 7. The heater 3 is in contact with the molybdenum disks 8 and 8', and then with matrices 1 and 1' through the current-carrying steel elements 9 and 9'so that the supply of electric power to the heater 3 can be accomplished through matrix 1 and 1' of the device. The top and bottom cell has an insulating washer 10 and 10', made of lithographic stone. The container 2 is surrounded by the outer ring 11 made of plastic material, for example PTFE.

Figure 2 shows a variant of the Assembly reaction cell in the high-pressure apparatus with thermocouple 12, scheme of registration of thermocouple readings with a voltmeter 13 and the scheme of supply of electric current to the heater 3 from the programmable source heating power 14. thermocouple is used for measuring temperature inside the reaction cell during the pre is kiteley camera calibration high pressure, temperature definition depending on the temperature of the heating power. Using a thermocouple also determine the time constant of the temperature relaxation in the cell, making records of the readings of thermocouple, for example, for a given step change of the heating power. The junction of thermocouple 12 is located inside the reaction volume, and its coming from the cell wires pass through the electrically insulating refractory tubes 15 and 15', which protect against contact wire thermocouple with graphite heater 3. The other designations figure 2 correspond to the positions of figure 1. Materials for thermocouple wire are platinum-rhodium alloys (thermocouple Pt30%Rh-Pt6%Rh).

Figure 3 shows examples of the experimental data obtained in high-pressure apparatus with an internal volume of the reaction cell ~3.6 cm3at a pressure of ~4 GPA: (a) calibration curve depending on the temperature of the heating power in the reaction cell, b) - dependence of the temperature in the reaction cell after switching off the heating power, the relaxation curves of the temperature in the cell from ~940°C to room temperature (taken as zero, since the cold junction of thermocouple was kept at room temperature). Data calibration on figa) to ~1800°C obtained using a thermocouple in quasi-stationary mode dimensions (with exposure time at each measurement point to obtain a hundred is ionamin values of temperature at a fixed heating power), while a higher temperature is obtained by recording the melting of aluminum oxide (the point on the graph when 2053°C) and metallic niobium (point on the graph at 2470°C). Experimental data for the relaxation temperature is presented on figb) points, the solid curve is the result of the regression analysis of these data. The inset graph shows the formula of the curve of temperature time, T(t)=938,8 exp(-t/30,94), and the value of the square of the correlation coefficient, R2=0,9992, which is very close to unity. The above graph shows that the relaxation of the temperature in the reaction cell at step off the heating power with high accuracy describes the exponential functional dependence of temperature on time:

T(t)=T0exp(-t/τ),

where T0- the initial value of the temperature (during shutdown of the heating power at t=0), and τ is the time constant of the relaxation temperature, which can be characterized by the transition process. In this case τ≈30,9 seconds. For understanding of the invention here illustrated, what is the meaning of the time constant of the relaxation of the temperature in the reaction cell of the high-pressure apparatus, and as the value of this constant can be determined experimentally. Note that at step turn on the heating power and the temperature in the cell with a high that is exactly what the article is described by the expression:

T(t)=Tm[1-exp(-t/τ)],

where Tm- temperature value, which is set in the cell during long-term exposure of a given heating power (when t>>τ and exp(-t/τ)<<1). In the literature, can meet different name and designation of the constant relaxation time. So, a similar expression as an approximation for the temperature in the chamber at step turn on the heating power is to address the problem of nonstationary heat conductivity given in the book: the Synthesis of minerals, Wehage, Liineburg, Limstella and others - M.: Nedra, 1987 (see volume 1, str), where the time constant of the relaxation temperature is called "thermal constant camera" and denoted by α. From the solution of heat conduction problem indicates a significant dependence of the time constant of the relaxation from the reaction cell sizes in different volume high-pressure cells (the time constant of the relaxation temperature is proportional to the square of the height of the reaction cell and is typically tens of seconds). Note that in accordance with the above formula for the time t, is equal to τ, the temperature in the cell at step enabling heating power reaches ~63.2% of Tmand for a time t equal to 3τ reaches ~95% of the Tm. Accounting for thermal "inertia" of the cell after the change (or change) the power is heating when determining the resulting temperature required for temporary periods of heating in the high temperature zone, comparable in duration to the magnitude 3τ. (In the present invention high temperature zone is the temperature range from 2000 to 2350°C.)

4 shows calculated curves of the temperature in the cell of a high pressure chamber depending on time (thin line) by the action of the heater different pulse heating: a) the pulse shape is rectangular, b) - pulse triangular - pulse sawtooth waveform (pulse forms are marked by bold lines). Line temperature response to pulses received, taking into account temperature relaxation in a cell on a defined change of the heating power when the pulse duration equal to 3,33τ (for triangular pulse is the duration of the symmetric half). The graphs explain the invention, they demonstrate the need to account for temperature relaxation when you set the temperature in the cell for heat output. During the process of short-term high-temperature heating of diamond crystals in the high-pressure apparatus are preferred scheme of heating shown in figv), for which the peak of the resulting temperature on the graph is more pronounced in comparison with gentle temperature maxima other heating schemes. In practice, when used for heating programmable source PI the project, typically, you set the speed of temperature rise in the cell, VTand the value of the maximum temperature, Tmon the calibration curve of the quasi-stationary regime. Calculations show that if we consider the temperature relaxation, the maximums specified temperature and are receiving the temperature in the cell can be significantly different from each other. For the circuit of heating shown in figv), the difference of values of maximum temperature, δ tm, (peak asked and obtained temperatures on the graph) is determined by the formula:

Δ tm=τVT.

As for the circuit of heating with the symmetric triangular peak set temperature, figb), the difference between the highs asked and obtained temperatures will correspond to the formula:

Δ tm=τVTℓn2.

More specifically, this can mean the following. For example, if we want to achieve in the cell temperature equal to 2100°C, With τ=30,9 C and VT=20°C/s, when using the circuit of heating shown in figv), we must specify the calibration curve is the maximum temperature at ~618°C higher than, equal to ~2718°C and scheme use of heating shown in figb), - is the maximum temperature at ~428°C higher than, equal to ~2528°C.

Figure 5 presents the generally accepted (see, for example, the Wikipedia page http://en.wikipedia.org/wiki/Diamond) prosanatatea chart carbon for explanation of the invention shaded area intended for treatment of a natural diamond brown on the proposed method. The area is located below the line of the graphite-diamond equilibrium in the region of thermodynamic stability of graphite and metastable existence of the diamond.

Below are examples of the application of the present invention. In the examples for the temperature treatment of the diamonds used a high-pressure apparatus with shaped matrices and the design of the reaction cell described above and presented in figure 1. The processing of diamonds in the examples was carried out at a pressure of ~4 GPA. The internal volume of the reaction cell was ~3.6 cm3. For the cell at the specified pressure using thermocouples Pt30%Rh-Pt6%Rh in the Assembly represented in figure 2, previously in quasi-stationary mode of measurements was obtained the temperature dependence of heat output presented on figa), and according to temperature changes in the cell when stepped off the heating power, figb), it was determined the value of the time constant of the relaxation temperature in the cell τ, which amounted to ~ 30,9 C. Heating of the cells was performed using a programmable digital power supply: Digital DC Power Supply XDC 10-600, Xantrex Technology Inc., whose own rise time (DL the required front) pulse is generated when the step change of power was less than 100 milliseconds.

Example 1. The diamond light-brown relating to the type IIA, weight is 3.08 carats and with the turning of faces in the form of "Marquise" with dimensions 16,77×of 6.68×4,91 mm, were placed in the reaction cell of the high-pressure chamber (in accordance with the Assembly of the parts represented in figure 1). Then in the camera using the hydraulic press has created a pressure of ~ 4 GPA and then carried out the heat treatment of diamond according to the scheme of heating can be found on figv), from the programmable power source of electric power with the speed of temperature rise of 15°C/s, up to a maximum temperature equal to 2670°C and required heating power in accordance with the curve of the calibration chamber temperature presented on figa). After reaching the specified maximum temperature of the heat source is automatically switched off. In this process, taking into account temperature relaxation in the cell was achieved temperature equal to ~2206°C (because it is less defined by the value of δ tm=τVT=30,9×15≈464°C), and the total time spent on the diamond crystal in the high temperature zone at temperatures higher than the temperature of 2000°C was ~17 seconds. After unloading the camera, the diamond was removed from the cell. In thermobaric treatment of the diamond turned into unpainted almost colorless crystal. On small areas of the surface the crystal formed traces its graphitization.

Example 2. The diamond light-brown relating to the type IIA, weight 4,33 carats and having the form of "Marquise" with dimensions 18,17×8,32×5,01 mm, were placed in the reaction cell of the high-pressure chamber in accordance with the Assembly of the components presented in figure 1. Then in the camera using the hydraulic press has created a pressure of ~4 GPA and then carried out the heat treatment of diamond according to the scheme of heating can be found on figv), from the programmable power source of electric power with the speed of temperature rise of 10°C/s, up to a maximum temperature equal to 2410°C and required heating power. After reaching the specified maximum temperature of the heat source is automatically switched off. In this process, taking into account temperature relaxation in the cell was achieved temperature equal to ~2101°C, and the total time spent on the diamond crystal in the high temperature zone at temperatures higher than the temperature of 2000°C was ~ 12 seconds. After unloading the camera, the diamond was removed from the capsules of the cell. In thermobaric treatment of the diamond turned into a nearly colorless crystal color group N on a scale developed by the Gemological Institute of America (GIA).

Example 3. Two brown diamond, one related to the type IIA, weight 4,01 carats and having the form of a "pear" with dimensions 13,57 the 8,58×5,63 mm, and the other related to the type of AAV, weight 3.39 carats and has the shape of a "pear" with dimensions 13,92×7,88×4,93 mm, were placed in one reaction cell, and simultaneously subjected to heat treatment by heating scheme presented on figv), at a pressure of 4.2 GPA. From the programmable power source electric power was set the speed of temperature rise of 15°C./s, and the maximum temperature value on the calibration curve, equal 2570°C. After reaching the specified maximum temperature of the power source is automatically switched off. In this process, taking into account temperature relaxation in the cell was achieved temperature equal to ~2106°C, and the total time spent on the diamond crystal in the high temperature zone at temperatures higher than the temperature of 2000°C was ~9 seconds. After unloading the camera diamonds were extracted from the capsules of the reaction cell. In the heat treatment of single crystal diamond has become almost colorless, and the other acquired a bright green-yellow color.

In some cases, the application of the proposed method of heat treatment of diamond diamond crystals dark brown related to type IIA, acquired a pink color. While most diamonds with brown hues related physical classification of types of IAA or AAV, acquired after treatment is otci yellow, yellow-green or green. The present invention allows high-temperature thermal processing of diamonds in high-pressure cells a large amount in the reaction cell a few samples or a single large crystal diamond weighing up to 20 carats.

Considering temperature relaxation during rapid heating and rapid cooling of the cell allows you to create short pulses of heat diamond in the high temperature zone, where there is a change brown crystals, and avoid graphitization of the diamond in the field of the metastable state of the diamond on the phase diagram of carbon.

1. The method of thermal processing of diamonds brown in the high-pressure chamber, comprising placing the diamond in the reaction cell in the environment, transmission pressure, a pressure rise in the chamber with subsequent heating of the reaction cell and its cooling, characterized in that the heat treatment is performed at a pressure in the chamber 3-6 GPA, and heating the reaction cell with diamond perform at the speed of rise of temperature 10-50°C/s to a temperature in the range 2000-2350°C by passing an electric current through the heater in the cell from the programmable source of electrical power with regard to the relaxation of the temperature in the cell in the heating process, and to decree the aqueous considering pre-determine the time constant of the relaxation of the temperature in the cell, and following the rise of the temperature of the cooling cell by turning off the heating power, forming a short pulse heating of a diamond in the zone temperatures above 2000°C, with a total residence time of the diamond in this zone of less than 30 C.

2. The method according to claim 1, characterized in that taking into account the relaxation of the temperature in the cell to the speed of temperature rise VTthe range 10-50°C/s and for a predetermined value of the time constant of the relaxation of the temperature in the cell τ carry out the job in the programmable power supply maximum heating temperature on the value of τVTabove the maximum temperature of heat treatment in the range 2000-2350°C.



 

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2 dwg

FIELD: process engineering.

SUBSTANCE: invention relates to production of abrasive tools intended for machining metals and alloys. Proposed cycle of processing AT at TTB comprises heating AT at 2450 Hz in microwave chamber for near-100 mm-thick AT and at 890-915 Hz for over-100 mm-thick AT to complete polymerisation (hardening) and curing semis at said temperature with uniform forced removal of volatile matters released therefrom (hot vapor-gas mix) from thermostat free volume by airflow created by exhaust vent system of microwave chamber via slots made in thermostat front and rear walls to rule out saturation of said volatile matters. Temperature of processed semis is controlled by device incorporated with thermostat and airflow forced in thermostat is heated to temperature of semis.

EFFECT: higher quality.

1 cl

FIELD: process engineering.

SUBSTANCE: invention relates to diamond processing, in particular, by thermochemical process. Proposed method comprises applying layer of spirit glue composition onto diamond surface, said composition containing transition metal, for example, Fe, Ni or Co, and processing diamond thermally at temperature not exceeding 1000°C. To prepare spirit glue composition, powder of water-soluble salt of transition metal is used. Said powder in amount of 1-10 wt % of water solution is mixed with spirit solution of glue at salt water solution-to-glue spirit solution ratio of 1:1. Prepared mix is applied on diamond surface in 10-20 mcm-thick layer to be dried. Thermal processing of diamond is performed in two steps. Note here that, at first step, diamond is processed at 600-700°C for 1-2 min, while, at second step, it is processed at 800-1000°C for 15-30 min.

EFFECT: superhigh specific surface with nano-sized (100-200 nm) relief, expanded applications.

2 dwg, 7 ex

FIELD: physics.

SUBSTANCE: method involves thermomechanical processing of initial crystalline material made from metal halides at plastic deformation temperature, obtaining a polycrystalline microstructured substance characterised by crystal grain size of 3-100 mcm and intra-grain nanostructure, where thermomechanical processing of the initial crystalline material is carried out in vacuum of 10-4 mm Hg, thus achieving degree of deformation of the initial crystalline material by a value ranging from 150 to 1000%, which results in obtaining polycrystalline nanostructured material which is packed at pressure 1-3 tf/cm2 until achieving theoretical density, followed by annealing in an active medium of a fluorinating gas. The problem of obtaining material of high optical quality for a wide range of compounds: fluoride ceramic based on fluorides of alkali, alkali-earth and rare-earth elements, characterised by a nanostructure, is solved owing to optimum selection of process parameters for producing a nanoceramic, which involves thermal treatment of the product under conditions which enable to increase purity of the medium and, as a result, achieve high optical parameters for laser material.

EFFECT: nanosize structure of the ceramic and improved optical, laser and generation characteristics.

3 cl, 3 ex

FIELD: machine building.

SUBSTANCE: procedure for surface of diamond grains roughing consists in mixing diamond grains with metal powder and in heating obtained mixture to temperature of 800-1100°C in vacuum as high, as 10-2-10-4 mm. As metal powders there are taken powders of iron, nickel, cobalt, manganese, chromium, their alloys or mixtures. Powders not inter-reacting with diamond grains at heating can be added to the mixture.

EFFECT: fabrication of diamond grains with optimal amount of recesses, possessing specified geometric parametres; reduced losses of diamond material and maintaining strength characteristics of grains.

4 cl, 1 dwg

FIELD: physics.

SUBSTANCE: method involves subjecting a grown and hardened, i.e. correctly annealed crystal, to secondary annealing which is performed by putting the crystal into a graphite mould, the inner volume of which is larger than the crystal on diameter and height, and the space formed between the inner surface of the graphite mould and the surface of the crystal is filled with prepared crumbs of the same material as the crystal. The graphite mould is put into an annealing apparatus which is evacuated to pressure not higher than 5·10-6 mm Hg and CF4 gas is then fed into its working space until achieving pressure of 600-780 mm Hg. The annealing apparatus is then heated in phases while regulating temperature rise in the range from room temperature to 600°C, preferably at a rate of 10-20°C/h, from 600 to 900°C preferably at a rate of 5-15°C/h, in the range from 900 to 1200°C preferably at a rate of 15-30°C/h, and then raised at a rate of 30-40°C/h to maximum annealing temperature depending on the specific type of the metal fluoride crystal which is kept 50-300°C lower than the melting point of the material when growing a specific crystal, after which the crystal is kept for 15-30 hours while slowly cooling to 100°C via step-by-step regulation of temperature decrease, followed by inertial cooling to room temperature.

EFFECT: high quality of producing monocrystals of metal fluorides owing to increase in their homogeneity with maximum reduction of defects in grown crystals, which ensures high yield of the material with good optical characteristics, use of a special mode of preparation and carrying out secondary annealing primary grown and hardened crystals of metal fluorides enable to eliminate microinhomogeneities and small-angle off-orientations of crystals.

1 ex

FIELD: electricity.

SUBSTANCE: method includes the first stage of increasing temperature of single-crystal substrate ZnTe up to the first temperature of thermal treatment T1 and maintenance of substrate temperature within specified time; and the second stage of gradual reduction of substrate temperature from the first temperature of thermal treatment T1 down to the second temperature of thermal treatment T2, lower than T1 with specified speed, in which T1 is established in the range of 700°C≤T1≤1250°C, T2 - in the range of T2≤T1-50, and the first and second stages are carried out in atmosphere of Zn, at the pressure of at least 1 kPa or more, at least 20 cycles or at least 108 hours.

EFFECT: invention makes it possible efficiently to eliminate part of Te deposits without considerable deterioration of efficiency and improvement of light transmission of single-crystal substrate ZnTe.

5 cl, 3 dwg

FIELD: chemistry.

SUBSTANCE: crystals are grown using the Kyropoulos method with an optimum annealing mode, carried out while lowering temperature of the grown monocrystal to 1200°C at a rate of 10-15°C/hour and then cooling to room temperature at a rate of 60°C/hour.

EFFECT: obtaining large monocrystals with less stress in the entire volume, and which are suitable for mechanical processing in order to obtain crystal wafers with zero orientation.

1 ex, 1 dwg

FIELD: chemistry.

SUBSTANCE: method involves crystallisation from molten mass through Stockbarger method and subsequently annealing the crystals through continuous movement of the crucible with molten mass from the upper crystallisation zone to the lower annealing zone while independently controlling temperature of both zones which are separated by a diaphragm. The crucible containing molten mass moves from the crystallisation zone to the annealing zone at 0.5-5 mm/h. Temperature difference between the zones is increased by changing temperature in the annealing zone proportional to the time in which the crucible moves from the beginning of crystallisation to its end, for which, while maintaining temperature in the upper crystallisation zone preferably at 1450-1550°C, in the lower annealing zone at the beginning of the crystallisation process temperature is kept at 1100-1300°C for 30-70 hours, thereby ensuring temperature difference of 450°C between the zones at the beginning. Temperature of the annealing zone is then lowered to 500-600°C in proportion to the speed of the crucible with the growing crystal. Temperature of the annealing zone is then raised again to 1100-1300°C at a rate of 20-50°C/h, kept for 18-30 hours after which the zone is cooled to 950-900°C at a rate of 2-4°C/h, and then at a rate of 5-8°C/h to 300°C. Cooling to room temperature is done inertially. Output of suitable monocrystals of calcium and barium fluorides with orientation on axes <111> and <001>, having high quality of transparency, uniformity, refraction index and double refraction is not less than 50%.

EFFECT: high output of suitable high-quality optical monocrystals for making photolithography optical elements.

FIELD: electricity.

SUBSTANCE: method includes placement of crystalline diamond nucleus in heat-absorbing holder made of substance having high melt temperature and high heat conductivity, in order to minimise temperature gradients in direction from edge to edge of diamond growth surface, control of diamond growth surface temperature so that temperature of growing diamond crystals is in the range of approximately 1050-1200°C, growing of diamond single crystal with the help of chemical deposition induced by microwave plasma from gas phase onto surface of diamond growth in deposition chamber, in which atmosphere is characterised by ratio of nitrogen to methane of approximately 4% N2/CH4 and annealing of diamond single crystal so that annealed single crystal of diamond has strength of at least 30 MPa m1/2.

EFFECT: increased strength.

26 cl, 4 dwg

FIELD: physics.

SUBSTANCE: proposed laser material is a ceramic polycrystalline microstructure substance with particle size of 3-100 mcm, containing a twinned nanostructure inside the particles with size of 50-300 nm, made from halides of alkali, alkali-earth and rare-earth metals or their solid solutions, with vacancy or impurity laser-active centres with concentration of 1015-1021 cm-3. The method involves thermomechanical processing a monocrystal, made from halides of metals, and cooling. Thermomechanical processing is done until attaining 55-90% degree of deformation of the monocrystal at flow temperature of the chosen monocrystal, obtaining a ceramic polycrystalline microstructure substance, characterised by particle size of 3-100 mcm and containing a twinned nanostructure inside the particles with size of 50-300 nm.

EFFECT: improved mechanical properties, increased microhardness and failure viscosity.

5 cl, 1 tbl, 4 ex, 1 dwg

FIELD: chemistry.

SUBSTANCE: synthetic diamonds are obtained by decomposition of solid carbonyl compounds of platinum metals in hermetic container at temperature 310°C-800°C during 1-2 hours with ratio of volumes of carbonyl compounds of platinum metals to container volume equal 1:1.1 to 1:100 in neutral atmosphere, further after opening container separation of diamonds from accompanying components is performed by treatment with aqua regia.

EFFECT: increased size of obtained diamonds.

5 tbl, 5 ex

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